Treatment of manganese and its alloys



@atented ay 21, 1940 TREATMENT OF GANEE AND HIS ALLQYS No Drawing. Application February 15, N39, Serial No. 253.45%

8 Claims;

My invention relates to methods of treating manganese and its alloys and is especially concerned with the treatment of manganese produced by reduction with silicon, aluminum or ii the like to convert it into suitable condition for use in making alloys with improved properties. The novel principles of my invention may also be employed in conjunction with the treatment of alloys containing a substantial proportion of manganese, generally of the order of at least 30% manganese.

I have found that alloys containing a relatively high proportion of manganese, as produced in accordance with prior art teachings by the employment of manganese produced by reduction with silicon or aluminum, are inferior to such alloys when produced from distilled or electrolytic manganese. This inferiority is particularly evident with respect to the properties of ductility and amenability to heat treatment.

In accordance with my invention, I have discovered that commercial grades of manganese, especially manganese which has been produced by reduction with silicon, may be greatly improved in its properties, at least so far as its use in alloys is concerned, by treatment with a fluoride, particularly an alkali metal fluoride such as sodium fluoride, potassium fluoride, or more complex fluoridessuch as cryolite. The effect upon the manganese may not be evidenced by chemical analysis in the ordinary way but is immediately evident in the properties of alloys made from the so treated manganese. The exact mechanism of the reaction has not been ascertained and I prefer, therefore, to base my invention upon actual and practical observations.

The following examples are illustrative of procedures for the treatment of manganese in ac= cordance with my invention. It will be understood that the proportions of the materials may be varied within reasonable limits, temperatures may be modified, and other changes may be made without departing from the invention.

Example 1 (Cl. lit-0) Example 2 (a) An alloy containing 15% chromium, 37% of manganese, and the balance essentially iron was made with a commercial silicothermic manganese containing, by analysis, 0.8% silicon.

(b) 100 pounds of this alloy was melted at a temperature of 1400 degrees C. to 1500 degreesC. and mixed with 7 pounds of cryolite for a period of 10 minutes. The alloy was then removed w from the cryolite and cast into suitable form.

As evidencing the important improvements which are brought about by the practice of my invention, I have taken an alloy containing 95% of commercial silioothermic manganese and 5% of copper. This alloy could not be not worked at 1000 degrees C. and then further reduced by cold rolling without surface cracking occurring. Furthermore, this alloy, on heating to 500 degrees C. for 15 minutes, became brittle and mechanically worthless. By preliminarily treating the manganese as described in Example 1 hereof and preparing the alloy from the resulting manganese so that the alloy contained 95% of such manganese and 5% copper, the following properties were observed: The alloy could be readily worked at 1000 degrees C. and could be cold rolled to small sizes without cracking. Furthermore, .the alloy hardened substantially on heating for 15 minutes at 500' degrees C. but did not become brittle. m

Another comparison may be made with respect to Example 2 hereinabove. The manganesechromium-iron alloy produced in part (a) thereof from commercial sillcothermic manganese was dimcult to hot and cold work and, after quenching from 1200 degrees C., cold working and reheating to 700 degrees C. for one hour, showed a hardness of ltd-35, The same alloy, after treatment, as described in part (b) of Example 2, could be readily worked hot and cold and, after quenching from 1200 degrees (3., cold working and reheating ior one hour at 700 degrees C... showed a hardness of Etc-55.

Similar results have been obtained by treatment of commercial manganese and alloys made (55 from it by means of sodium fluoride and other alkali metal fluorides.

In addition to the improvements'which the practice of my invention brings about, as set forth hereinabove, I have found that the chemical activity of the manganese is substantially increased. 7

- The proportions of". fluoride may be varied within relatively wide limits. In general, be-

tween 5% and 10% by weight of the manganese or alloy made therefrom is efiective although lesser or greater amounts may be employed. 'The temperature of treatment is also capable of variation although, in all cases, the manganese or alloy made therefrom is treated with the fluoride while in a melted or molten condition. A satisfactory temperature for treatment of the manganese or its alloys with the fluoride is of the order of degrees C. to degrees C. above the melting point of the manganese or the alloys made therefrom.

What I claim as new and desire to protect by Letters Patent of the United States is:

1. A method of treating commercial manganese which has been reduced at least in part by silicon or aluminum to render it more suitable for the preparation of alloys which comprises contacting saicl manganese, in a molten condition, with an alkali metal fluoride for at least several minutes.

2. A method of treating commercial manganese which has been reduced at least in part by silicon or aluminum to render it more suitable for the preparation of alloys which comprises contacting said manganese, in a molten condition, with cryolite for at least several minutes.

3. A method of treating a member selected from the group consisting of commercial manganese which has been reduced atleast in part by silicon or aluminum and alloys containing at least 30% of such commercial manganese which comprises subjecting the same, in a molten condition, to relatively intimate contact with an alkali metal fluoride.

4. A method of treating a member selected from the group consisting of commercial manganese which has been reduced at least in part by silicon or aluminum and alloys containing at least 30% of such commercial manganese which comprises subjecting the same, in a molten condition, to relatively intimate contact with cryolite for a period of at least several minutes.

5. A method of treating commercial silicothermic manganese to render the same more suitable for the preparation of alloys which comprises contacting said manganese, in a molten condition, with cryolite.

6. A method of treating commercial aluminothermic manganese torender it more suitable for the preparation of alloys which comprises contacting said manganese, in a molten condition, with an alkali metal fluoride.

7. A method of treating a member selected from the group consisting of commercial manganese which has been reduced at least in part by silicon or aluminum and alloys containing relatively large proportions of such manganese which comprises subjecting the same, in a molten condition, to relatively intimate contact with from about 5% to 10% by weight of an alkali metal fluoride.

8. A method of treating commercial silicothermic manganese which comprises subjecting the same, in a molten condition, to relatively intimate contact with from about 5% to about 10% of its weight of cryolite.

Y nueannrn t3. DEAN. 

